The SCART connector was developed by the French. Its original purpose was to prevent foreign television imports. Previously France had legislation which prevented all imported televisions, if they didn't support the old French 819 line monochrome system. One could understand that this effectively stopped any foreign televisions being imported, but when the 819 line system disappeared this was no longer a valid reason for banning imports. Therefore they introduced the SCART socket to try and maintain their private television market, the newly passed legislation requiring every TV sold in France since 1980 to have a SCART socket. This was of course much less of a deterrent, as it was much easier for manufacturers to add a SCART socket to their televisions than to produce dual-standard sets, and the SCART was actually useful elsewhere with the development of cheap home video recorders.
Before SCART, many video and audio devices provided lots of different sockets for AV signals. Devices made by different companies could have different and incompatible standards.
SCART attempts to make connecting such devices together much simpler, by providing one plug that contains all the necessary signals, and is standard across different manufacturers. SCART makes connecting such devices very simple, because one cable can connect any two SCART-compatible devices, and the connector is designed so that you cannot insert it incorrectly.
Pin-out:
+------------------------------------------+ | 1 3 5 7 9 11 13 15 17 19 | 21 | \\ | 2 4 6 8 10 12 14 16 18 20 \\ +--------------------------------------------+AUDIO Output Right